Wire insulation stripper



1949- J. E. WOOLMAN 2,477,678

WIRE INSULATION STRIPPER Filed Feb. 8, 1945 ;as shown in Figure Patented Aug. 2, 1949 WIRE INSULATION STRIPPER James E. Woolman, United States Army, Elkton, Md.

Application February 8, 1945, Serial No. 576,867

(Granted under the act of March 3, 1883, as

'7 Claims.

amended April 30, 1928; 3'70 0.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention concerns a wire insulation stripper.

It is an object of the invention to provide means whereby insulation may be readily removed from wire or the like to be used in electric circuits.

It is an object of the invention to provide an insulation stripper for readily and rapidly removing the insulation from the high tension leads in an aeroplane engine or the like.

It is an object of the invention to construct a wire insulation stripper to be utilised with stranded high tension leads whereby the insulation may be stripped from a given measured length of an end of the lead without nick-ing any strand thereof.

It is an object of the invention to provide means to remove the insulation from a stranded conductor intended to carry high frequency current at high voltage without the danger of leakage and resultant radio interference caused by nicking one or more of the strands of the conductor.

It is an object of the invention to provide means to remove measured lengths from the end of stranded conductors in a minimum of time and without the care and skill normally required when such an operation is performed by hand.

It is an object of the invention to provide a wire insulation stripper which is cheap and sturdy in construction and which may readily be built from materials at hand.

Reference will be had to the drawings in which one form the invention may take is disclosed. Like numbers refer to like parts throughout.

Figure 1 is a perspective view of an assembly of the device.

Figure 2 is a plan in Figure 1.

Figure 3 is a side elevation of the invention.

Figure 4 is an end elevation of the invention with its mounting indicated.

Figure 5 is a plan view of the lower base block of the device.

Figure 6 is a side elevation of of the device.

Figure '7 is a plunger .pin detail.

Base block I is a lower section of the device which has a step-like break in its bottom side, whereby it is provided with an enlarged portion II and a thin portion l2. A central longitudinal fin 13 extends along thin porview of the invention shown the upper block tion l2 of said base block [0 toward the enlarged portion ll, being spaced therefrom as at [4. Fin I3 is somewhat thicker than the diameter of the wire or cable to be stripped, but is considerably thinner than the diameter of the insulation. The enlarged portion H has a central longitudinal passage l5 ther-ethrough adjacent the lower surface thereof and aligned with fin l3 as shown in Figure 4.

On the side of base block Ill opposite fin 13, but extending into that part comprising enlarged portion H are two spaced V-shaped slits l6 and I1. Slits l6 and I1 are positioned respectively one and one and a half inches from the end of fin l3, and extend downwardly into passage l5. Holes I8 and I9 are provided in the same face of base block [0 as slits l6 and I1 and positioned centrally of said slits respectively. Holes l8 and I9 stop short of passage 15. A hole extends through the base block Ill adjacent the centre thereof and parallel to hole 18. The lower portion of hole 20 is counterbored as at 2| forming enlarged opening 2| positioned adjacent space [4. Threaded holes 22 and 23 are provided at each end of base block [0 for assembly purposes. An upper mating portion 24 is provided with counter-sunk holes 25 and 26 whereby it may be attached by machine screws or the like to base block Ill. Slots 21 and 28 are positioned to mate with wedge-shaped slits l6 and i1 respectively. Said slots are of considerable depth and extend entirely across upper portion 24 but are wider than the slits to provide shoulders or abutments l6 and 11' at the top of the slits. Holes 29 and 30 are contained in upper portion 24 in such position as to register with and to form a continuation of holes 18 and I9 respectively. Hole 3| extends through upper portion 24 and is likewise positioned to register with and form a continuation of hole 20 in base block l0. Transverse holes 32 and 33 are provided in upper portion 24 for mounting purposes as will hereinafter appear.

. A plunger 34 is provided with an enlarged head 35 and a shank 33 of such diameter as to slide freely in holes l8 and 19. The bottom portion of plunger 34 has a longitudinal slot 37 of such size as to snugly receive the head of a single. edged razor blade 38 inserted endwise into the slot from the side of the plunger. A narrow slotted portion 39 permits the blade portion to project from the end of plunger 34 and provides shoulders 40 which bear against the under side of the head portion of the razor blade and hold it in position. A similar unslotted plunger 4| fits hole 20. Plungers 34 and 4| are provided with compression springs 42. Plunger 4| may have a ring 43 or the like pressed on its lower end and of such size as to seat in counterbore 2|, holding plunger 4| in position with its spring 42 slightly compressed. Plungers 34 in holes [8 and H! are held in position with the razor blades clear of the passage H: by the action of the compression springs 42, the outward movement of each plunger being stopped while the spring is under slight compression by the abutment of the top or head of the razor blade with the upper wall of its confining slot 21 or 28 against which it is held by the action of the shoulders 40 of the plunger on the underside of the head portion of the blade. Mounting rods 44 and 44 extend through and are slidable in holes 32 and 33 and carry side mounting plates 45 and 46 on their outer ends. Mounting plates 45 and 46 have lower diverging extensions 4'! and 48 respectively arranged to fit the standing edges on a jewellers jaw vise. Spring clip portions 49 and '50 are mounted 'onthe inner sides of plate members 45 and 46 and bear upon upper portion '24. Cotter pins '51 in rods "44 and 44 hold this portion of the assembly together.

The device is mounted by means of screws through diverging extensions 41 and 48 on a jaw vi's'e of small size su'c'h'as that commonly used by jewellers and the like. After the cutting operation the jaws of the vise are tightened so as to grip downwardly extending fin l3 and the cable insulation firmly. It will be noted that while the insulation is gripped firmly by the vise and compressed somewhat thereby, the relative size of the diameter of the metallic conductor and the thickness of fin l3 prevent "the clamping action ofthe'vise jaws from gripping the metallic conductor itself. Diverging flange-like portions 41 and 48 bear against'the sloping sides'of the jaws of the vise and cause springs 49 and 50 to press againstupper portion "24, thus firmly mounting the assembly and holding it in position when the vise is loosened for the -insertion of cable. The operation of the device is as follows:

The end of a'wire to be stripped 'is inserted in the hole l until it t'ouch'e's'the end of fin l"3. As noted above the present deviceis particularly intended for high tension leads to "the spark plugs of aircraft engines and the like. This wire is of special'manuiacture, quite'expensive and usually stranded. In most installation an exact length of stripped wire'is desired to make 'a' connection. Should this length be exceeded an undesirable exposure of conductorwilloccurwith a danger of short circuit. Should this length be insuificient a faulty joint or connection may be made which may subsequently result'in engine failure.

If'for'agiven installation it'is desired-to strip onein'ohof insulation from the end of the lead, the first plunger 34 'or'thatin hole IBis pressed downwardly so that the razor blade held in slot 38 in' thelower, portionof shank '36 is forced down almost through the insulation of the cable-or conductor, the downward movement ofthe plunege'r being halted by 'theabutment'of the lower edges of thehead portion of'the razor blade with the shoulders or'stops at the'top of the slits l'6 'at'which time the cutting edge of the bladeshall 'have' penetrated the insulation to'a point adjacent but short of contact with 'themetallic' cable or conductor. The edge of the'razor bladeslides into V slits I6 which acts as a supporting guide. While the plunger '34'is depressed the'cable or conductor is rotated through 360 thusmakin'g a clean out through the insulationentirely"around the'cond'uctor. It is particularly'tobe' notedthat 4 this operation does not raise a burr or other projection upon the metallic strands of the cable through which the leakage or high frequency high tension emanations may occur and int-erfere with radio reception.

When the complete peripheral cut is made the plunger 34 is released and rises under the action of spring 42, carrying the razor blade with it so that the blade entirely clears the cable insulation. The jaws of the vise are tightened and the cable is then withdrawn. The cut portion of insulation is held by the jaws of the vise and comes 'oii cleanly leaving a square edge insulation on the cable. The jaws of the vise are then released and plunger-4l is depressed in hole 20 to eject the stripped cable portion. The device is now ready to strip the next lead. Should it be desired to strip an inch and a half of insulation the plunger in hole I 9 is depressed and the operation described above repeated. It will be noted that the positioning of holes I 8, T9 and 20 from the end of the fin ['3 will be determined by the particular job that is desired to be done. For most purposes in airplane work an inch and an inch and a half are satisfactory stripped lengths.

If desired spring portions 49 and may be eliminated and the mounting rods "44- and 44' press fitted into holes 32 and 33. For this purpose the central 'portion's of mounting 'rods '44 and 44 maybe roughened somewhat. The function of spring clip portions '49 and'50 is to centre the base block in the open'space between the jaws :of the vise so thatan edge portionof a jaw will not interfere with the insertion of 'a piece-of cable-to be'stripped. When mounting rods '44 1 and 44' are press fitted as above described, it willbe'seen that upon opening the vise that-the action ofm'ounting'plates'45 and '46 on cotter pins 5| serves .to centre base block l0 in such a manner that :no interference is experienced from the jaws of "the vise.

Having thus described the invention what :is claimed is:

1. A wire-insulation stripper comprising 'a -body having a longitudinal passage for the insertion of the insulated end of the wire to be strippedand having a transverse -slot'extendingintoithe passage'and having a-bore positioned centrallyof the-slot and terminating short of the passage, said "slot having its open ends -at the side 1 of the body andbeing of a'widthan'd depth to slidably accommodate a conventional single edge razor blade inserted endwise therein through either of its open ends, a plunger mounted on the body for movement in-a plane normal "to the passage and'having a slotted 'portion'disp'osed in -the bore to receive andsup'port the razor blade-withits cutting edge disposed passageward, "tension means associated withthe'plun'ger and normally holding the latter and the cutting edge of the blade'outwa'rdly displace'd with' respect to'the passage, said plunger being movable against -the resistance of "the "tension m'ean's =to "cause the 'cuttin'g-edgeof the blade to penetrate 'theepassage, and blade-abuttingmeans located' in 'the slot toengage and abut-the undersid'eiof the head portion of the razor blade for limiting th'e cutting action of 'theblade to the insulation aroun'd' the wire.

2 A wire insulationstripper-comprising abody having a longitudinal passage for the insertion of the insulated end of'the wire'to' be stripped and having-a transverse 'slot"extending entirely across the portion" of the'body between the said passage and the upper surface of the -bo'dy and forming lateral openings in the body, the said slot comprising an upper rectangular portion of a width and depth to slidably accommodate a conventional single edge razor blade inserted endwise therein through either of the said lateral openings in the body and an inner portion converging to form a V-shaped slit extending into the passage, a movable blade carrier mounted on the body for movement in a plane normal to the passage and having a laterally and downwardly slotted portion disposed in the upper portion of the slot to receive and support the razor blade with its cutting edge disposed passageward and within the V-shaped slit of the lower portion of the slot, tension means associated with the blade carrier and normally holding the latter and the cutting edge of the blade outwardly displaced with respect to the passage, said carrier being movable against the resistance of the tension means to cause the cutting edge of the blade to penetrate the passage, and blade-abutting means located in the slot and at the top of the V-shaped slit to engage and abut the underside of the head portion of the razor blade for limiting the cutting action of the blade to the insulation around the wire.

3. A wire insulation stripper comprising a body having a longitudinal passage extending therethrough adjacent the lower surface thereof for the insertion of the insulated end of the wire to be stripped and having a transverse slot between the passage and the upper surface of the body and extending into the passage from one side thereof, said slot having its open ends at the sides of the body and being of a width and depth at its upper portion to slidably accommodate a conventional single edge razor blade inserted endwise therein and converging at its lower portion to provide a V-shaped slit in which the cutting edge of the blade is adapted to be received and guided, a movable blade carrier mounted on the body for movement in a plane normal to the passage and having a slotted portion disposed in the upper portion of the slot to receive and support the razor blade with its cutting edge extending into the V-shaped slit, and tension means associated with the blade carrier and normally holding the carrier and the blade outwardly displaced with respect to the passage with the cutting edge of the blade entirely clear of the passage, said carrier being movable against the resistance of the tension means to cause the cutting edge of the blade to penetrate the passage, the said slot having walls of its upper portion offset relative to the walls of its lower portion to provide bladeabutting shoulders located in the slot at the top of and on opposite sides of the V-shaped slit to engage and abut the underside of the head portion of the razor blade for limiting the cutting action of the blade to the insulation around the wire.

4. A wire insulation stripper comprising a body having a step-like break on one side thereof whereby it is provided with a thick portion and a thin portion, the said thick portion having a longitudinal passage for the insertion therethrough of the end of the insulated wire to be stripped, said passage opening out upon the said thin portion of the body, a stop on the thin portion of the said body and in alignment with but spaced from the passage to be engaged by the end of the wire subsequent to the emergence of the said end of the wire from the passage, the thickness of said stop being greater than the diameter oi the wire to be stripped but less than 6 the diameter of the insulation to be removed, cutter means mounted on the thick portion of the body and movable into the passage for cutting the insulation of the inserted wire, and means associated with the thin portion of thelbody for mount-.

ing the stripper on a vise and including mounting members on opposite sides of the thin portion of the body and extending downwardly below the stop for engagement with the jaws of the vise, said mounting members being movable relatively to the body in a plane normal to the sides of the said thin portion and having diverging lower extensions to fit the standing edges of the vise and to be secured thereto for positioning the stripper on the vise so that adjacent portions of the stop and the space between the latter andthe pas-- sage are in the path of movement of the jaws of the vise whereby the insulation of the inserted wire exposed in said space will be clamped and compressed between th jaws of the vise when the said jaws are tightened to grip the said stop,the size differential between the wire and the stop preventing the gripping action of the jaws from clamping the wire and permitting the latter to be withdrawn from the body subsequent to the cutting operation leaving the cut and stripped portion of the insulation between the jaws of the vise.

5. A wire insulation stripper comprising a body having a passage for the insertion therethrough of the end of the insulated wire to be stripped of the insulation, cutter means associated with the body and movable into the passage for cutting the insulation of the inserted wire, and a relatively thin fiat plate associated with the body and positioned thereon in alignment endwise with but spaced axially from a terminal end of the passage with the end nearest the passage forming a stop to be engaged by the end of the inserted wire subsequently to the emergence of the said end of the wire from the said end of the passage whereby the portion of the insulated wire between the stop and the passage is in an exposed position adapting it to be gripped and held jointly with the stop by a clamping device, said plate having opposite side faces of substantial area to be gripped by a clamping device and separated by a thickness of material greater than the diameter of the wire to be stripped but less than the diameter of the insulation to be removed to prevent the gripping action of the clamping device from clamping and holding the wire against withdrawal from the body, whereby when said wire is withdrawn through the passage subsequent to the cutting and clamping operations the cut portion of the insulation will be retained by the clamping device and stripped from the wire.

6. A wire insulation stripper comprising a body provided on one side with a passage for the insertion therethrough of the insulated end of the wire to be stripped, a longitudinal fin on the body in line with but spaced from the passage to provide an abutment for the end of the inserted wire, said longitudinal fin being thicker than the diameter of the wire but considerably thinner than the diameter of the insulation on the wire, cutting means associated with the body and movable into the passage for cutting the insulation, mounting rods extending transversely through the body above and normal to the plane of the fin, mounting plates slidable on said rods and having lower diverging extensions adapted to be engaged with and fastened to the jaws of a vise for holding the stripper in position thereon with the fin between and in the path of movement of ammm the: jawma spring members: carriefi by the: plates:

ductorcomprising a; body; having: a step like' on onez-sidethereof whereby itis providedwith QE-thiCK-pOEtiOD and ak-thinportion said thick. portionha'vi-ng; a; conduetor r'eceiving passagee'xtend-ingrlongi-tudinal ly thereth'rough andopening ou-t upen the: thin port-ion; gaugingmeans as soeiatedf withihesaid thin-body portion and-supported thereby in longitudinally'spaced-relatibmto the thick port-ion: of the b'ody but in alignment with the said passage: to be-engaged by: the:end of the co'nductdn subsequent to its: emergence from the passage," cutting: means .assoeiataf with thethick-portium of--the body anciemovable into'- the:

said: passage-w contact and-cub: the insuiakion ofthtficiondubtor, and ejector-means-associated-w1th therthin'portion or: the=b0dy'and1- movable into the spa-cebetween; the gauging means and the thick por ion ofthe body to engage andeject thestripped -portion of: insulationa JAMES E:

R/EFERENGES ITED- Thefdlldwing refreme am 0f rec'ord'in the:

N'umber Name 75291857 Hutemh'gs Apr; 1=2;'1 904 9691339 c'hvtraas Sept; 6',- 1- 91-0-' 111655173 Hbrno'r' De'. 21 1-915 11680i789 Jaeofisofi Aug; 14,1928 210%?95774- Wacristeifi Aug-1 Ivy-1937* 231201398 Eiivvards June 14,1938 233851951 SteTz'ef o'ce; 2; 1945 

